Fiber structure and fiber structure block

ABSTRACT

Provided is a fiber structure including: cellulose fiber disposed such that a main fiber orientation direction is a first direction; and a crosslinking material that binds a plurality of the cellulose fibers to each other, in which the first direction forms an angle of equal to or less than 45 degrees with respect to a direction of an external force applied from an outside to a bottom surface.

The present application is based on, and claims priority from JP Application Serial Number 2019-171302, filed Sep. 20, 2019, the disclosure of which is hereby incorporated by reference here in its entirety.

BACKGROUND 1. Technical Field

The present disclosure relates to a fiber structure and a fiber structure block.

2. Related Art

In the related art, a method for manufacturing a plate-shaped material made of fiber by overlapping nonwoven clothes is known (see International Publication No. 2007/018051, for example).

Packaging materials using fiber have an advantage that they have a less environmental burden than packaging materials made of styrofoam or the like. However, it is difficult to allow the packaging materials using fiber to have a buffering effect against impact.

SUMMARY

According to an aspect to achieve the aforementioned object, there is provided a fiber structure including: a cellulose fiber disposed such that a main fiber orientation direction is a first direction; and a crosslinking material that binds a plurality of the cellulose fibers to each other, each of which is the cellulose fiber disposed such that the main fiber orientation direction is the first direction, in which the first direction forms an angle of equal to or less than 45 degrees with respect to a direction of an external force applied from an outside to an outer surface of the fiber structure.

According to an aspect to achieve the aforementioned object, there is provided a fiber structure including: a cellulose fiber disposed such that a main fiber orientation direction is a first direction; and a crosslinking material that binds a plurality of the cellulose fibers to each other to each other, each of which is the cellulose fiber disposed such that the main fiber orientation direction is the first direction, in which the fiber structure has an accommodation space that accommodates an accommodated article, and the first direction forms an angle of equal to or less than 45 degrees with respect to a direction of an external force applied from an outside of the fiber structure toward the accommodation space.

In the aforementioned fiber structure, the first direction may be a direction that forms an angle of equal to or less than 45 degrees with respect to the direction of the external force applied directly to the outer surface of the fiber structure or applied to the outer surface of the fiber structure via an external member.

The aforementioned fiber structure may include a plurality of the outer surfaces, each of which is the outer surface to which the external force is applied from the outside, and the first direction may form an angle of equal to or less than 45 degrees with respect to a normal line of any one of the outer surfaces.

In the fiber structure, the first direction may form an angle of equal to or less than 45 degrees with respect to a normal line of a largest outer surface of the plurality of outer surfaces.

In the aforementioned fiber structure, the crosslinking material may contain a first resin and a second resin made of a material that is different from the first resin.

The aforementioned fiber structure may include a material that is different from the cellulose fiber and the crosslinking material.

The aforementioned fiber structure may be configured of a flat plate structure in which the cellulose fibers are laminated, and the first direction may be a direction included in a plane of the flat plate structure.

According to an aspect to achieve the aforementioned object, there is provided a fiber structure block including: a plurality of combinations of fiber structures each including a cellulose fiber disposed such that a main fiber orientation direction is a first direction, and a crosslinking material that binds a plurality of the cellulose fibers to each other, each of which is the cellulose fiber disposed such that the main fiber orientation direction is the first direction, in which the fiber structure block has an accommodation space that accommodates an accommodated article, and the fiber structures are disposed such that the first direction forms an angle of equal to or less than 45 degrees with respect to a direction of an external force applied from an outside toward the accommodation space.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a configuration diagram of a sheet manufacturing apparatus.

FIG. 2 is a flowchart illustrating a manufacturing step of a fiber structure.

FIG. 3 is an explanatory diagram of a fiber orientation direction in a sheet.

FIG. 4 is an explanatory diagram of a fiber orientation direction in a sheet.

FIG. 5 is a diagram illustrating a configuration of a test piece for testing a buffering function.

FIG. 6 is a chart illustrating test results of the buffering function.

FIG. 7 is a schematic diagram illustrating an expression state of the buffering function.

FIG. 8 is a perspective view illustrating an example of a fiber structure.

FIG. 9 is a perspective view illustrating another example of the fiber structure.

FIG. 10 is a sectional view taken along the line X-X in FIG. 9.

FIG. 11 is a perspective view illustrating still another example of the fiber structure.

FIG. 12 is a diagram illustrating a configuration example of a composite sheet.

FIG. 13 is a diagram illustrating a configuration example of a composite sheet.

FIG. 14 is a diagram illustrating a configuration example of a composite sheet.

FIG. 15 is a diagram illustrating a configuration example of a composite sheet.

FIG. 16 is a schematic diagram illustrating a molding portion according to a second embodiment.

FIG. 17 is a perspective view illustrating an example of a fiber structure according to the second embodiment.

FIG. 18 is a sectional view taken along the line XVIII-XVIII of FIG. 17.

FIG. 19 is a perspective view illustrating another example of the fiber structure according to the second embodiment.

FIG. 20 is a perspective view illustrating still another example of the fiber structure according to the second embodiment.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Hereinafter, preferred embodiments of the present disclosure will be described in detail with reference to drawings. Note that the embodiments described below are not intended to limit details of the present disclosure described in aspects. In addition, all of the configurations described below are not necessarily essential components of the present disclosure.

1. First Embodiment 1-1. Sheet Manufacturing Apparatus

FIG. 1 is a diagram illustrating a configuration of a sheet manufacturing apparatus 100. The sheet manufacturing apparatus 100 manufactures a sheet S1 which is a material of a fiber structure to which the present disclosure is applied.

The sheet manufacturing apparatus 100 includes a supply portion 10, a crushing portion 12, a defibrating portion 20, a sorting portion 40, a first web forming portion 45, a rotating body 49, a mixing portion 50, a dispersing portion 60, a second web forming portion 70, a web transport portion 79, a processing portion 80, and a cutting portion 90.

The sheet manufacturing apparatus 100 fiberizes a raw material MA containing fiber, which will be described later, such as a wood pulp material, kraft pulp, waste paper, and synthetic pulp to manufacture the sheet S1.

The raw material MA may be any one containing a cellulose fiber. For example, a wood pulp material, kraft pulp, waste paper, synthetic pulp and the like can be used. Examples of the wood pulp materials include mechanical pulp that is made by a mechanical process such as ground pulp, chemical pulp that is made by a chemical process, and semi-chemical pulp and chemiground pulp that are manufactured by using both of these processes. Also, the wood pulp material may either bleached pulp or non-bleached pulp. Examples thereof include virgin pulp such as bleached softwood kraft pulp (N-BKP) and bleached hardwood kraft pulp (L-BKP) and bleached chemi-thermo mechanical pulp (BCTMP). Also, a nano-cellulose fiber (NCF) may also be used. The waste paper is used paper such as plain paper copy (PPC) paper after printing, magazines, and newspapers. Examples of the synthetic pulp include SWP manufactured by Mitsui Chemicals, Inc. SWP is a registered trademark.

Also, the raw material MA may contain carbon fiber, metal fiber, or thixotropic fiber in addition to or instead of the aforementioned wood pulp material, waste paper, synthetic pulp and the like. Therefore, the raw material MA may be a mixture obtained by mixing a plurality of materials selected from the aforementioned wood pulp material, waste paper, synthetic pulp, carbon fiber, metal fiber, and thixotropic fiber.

It is possible to state that the raw material MA and a defibrated material MB and a fiber material MC, which will be described later, are materials containing fibers.

The supply portion 10 supplies the raw material MA to the crushing portion 12. The crushing portion 12 is a shredder that cuts the raw material MA by using a crushing blade 14. The raw material MA cut by the crushing portion 12 is transported to the defibrating portion 20 through a pipe.

The defibrating portion 20 defibrates the fine pieces cut by the crushing portion 12 into defibrated material MB by a dry method. The defibration is a process of disentangling the raw material MA in a state in which a plurality of the fibers are bound into one or a few fibers. The dry method refers to performing a process such as defibration in gas, such as in the air, instead of in a liquid. The defibrated material MB includes the fiber contained in the raw material MA. The defibrated material MB may include substances other than the fiber contained in the raw material MA. When waste paper is used as the raw material MA, for example, the defibrated material MB contains constituents such as resin particles, a colorant such as ink or a toner, an anti-bleeding agent, and a paper strengthening agents.

The defibrating portion 20 is, for example, a mill including a tubular stator 22 and a rotor 24 that rotates inside the stator 22, and defibrates the crushed pieces with the crushed pieces sandwiched between the stator 22 and the rotor 24. The defibrated material MB is sent to the sorting portion 40 through a pipe.

The fibers contained in the raw material MA or the fibers contained in the defibrated material MB have a fiber length of equal to or greater than 0.1 mm and equal to or less than 100 mm, and preferably have a fiber length of equal to or greater than 0.5 mm and equal to or less than 50 mm. Also, the fiber diameter of the fiber is equal to or greater than 0.1 μm and equal to or less than 1000 μm, and is preferably equal to or greater than 1 μm and equal to or less than 500 μm. The fiber may include a plurality of types of fiber, and may include fiber with different fiber lengths and/or fiber diameters. The fiber lengths and the fiber widths can be obtained by performing measurement with a fiber tester (manufactured by Lorentzen & Wettre), for example, and calculating length weighted average values therefrom.

The sorting portion 40 has a drum portion 41 and a housing portion 43 that accommodates the drum portion 41. The drum portion 41 is a sieve having openings such as a net, a filter, or a screen and is rotated by power of a motor, which is not illustrated. The defibrated material MB is loosened inside the rotating drum portion 41 and is lowered through the openings of the drum portion 41. Substances that do not pass through the openings of the drum portion 41 among the constituents of the defibrated material MB are transported to the defibrating portion 20 through a pipe.

The first web forming portion 45 includes an endless mesh belt 46 having a large number of openings. The first web forming portion 45 manufactures a first web W1 by accumulating fiber and the like lowered from the drum portion 41 on the mesh belt 46. Substances that are smaller than the openings of the mesh belt 46 among the constituents lowered from the drum portion 41 are suctioned and removed by a suctioning portion 48 through the mesh belt 46. In this manner, fiber that is short and is not suitable for manufacturing of the sheet S1, resin particles, ink, a toner, an anti-bleeding agent, and the like among the constituents of the defibrated material MB are removed.

A humidifier 77 is disposed on a movement path of the mesh belt 46, and the first web W1 accumulated on the mesh belt 46 is humidified by mist of water or high-humidity air.

The first web W1 is transported by the mesh belt 46 and comes into contact with the rotating body 49. The rotating body 49 divides the first web W1 by a plurality of blades to form the fiber material MC. The fiber material MC is transported to the mixing portion 50 through a pipe 54.

The mixing portion 50 includes an additive supply portion 52 that adds an additive material AD to the fiber material MC and a mixing blower 56 that mixes the fiber material MC and the additive material AD. The additive material AD will be described later.

The mixing blower 56 generates an air flow in the pipe 54 in which the fiber material MC and the additive material AD are transported, mixes the fiber material MC and the additive material AD, and transports a mixture MX to the dispersing portion 60.

The dispersing portion 60 includes a drum portion 61 and a housing portion 63 that accommodates the drum portion 61. The drum portion 61 is a cylindrical sieve configured similarly to the drum portion 41 and is driven and rotated by a motor, which is not illustrated. The mixture MX is disentangled through the rotation of the drum portion 61 and is then lowered inside the housing portion 63.

The second web forming portion 70 includes an endless mesh belt 72 having a large number of openings. The second web forming portion 70 manufactures a second web W2 by accumulating the mixture MX lowered from the drum portion 61 on the mesh belt 72. Substances that are smaller than the openings of the mesh belt 72 among the constituents of the mixture MX are suctioned by a suctioning portion 76 through the mesh belt 72.

A humidifier 78 is disposed on a movement path of the mesh belt 72, and the second web W2 accumulated on the mesh belt 72 is humidified by mist of water or high-humidity air.

The second web W2 is peeled off from the mesh belt 72 by the web transport portion 79 and is transported to the processing portion 80. The processing portion 80 includes a pressurizing portion 82 and a heating portion 84. The pressurizing portion 82 nips the second web W2 by a pair of pressurizing rollers and pressurizes the second web W2 with a predetermined nip pressure to form a pressurized sheet SS1. The heating portion 84 applies heat to the pressurized sheet SS1 with the pressurized sheet SS1 nipped by a pair of heating rollers. In this manner, the fibers contained in the pressurized sheet SS1 are bound to each other by the resin contained in the additive material AD, and a heated sheet SS2 is thus formed. The heated sheet SS2 is transported to the cutting portion 90.

The cutting portion 90 cuts the heated sheet SS2 in a direction intersecting a transport direction FE and/or a direction along the transport direction FE to manufacture the sheet S1 with a predetermined size. The sheet S1 is stored in a discharge portion 96.

The sheet manufacturing apparatus 100 includes a control device 110. The control device 110 controls each part of the sheet manufacturing apparatus 100 including the defibrating portion 20, the additive supply portion 52, the mixing blower 56, the dispersing portion 60, the second web forming portion 70, the processing portion 80, and the cutting portion 90 and causes the parts to execute the method for manufacturing the sheet S1. Also, the control device 110 may control operations of the supply portion 10, the sorting portion 40, the first web forming portion 45, and the rotating body 49.

The additive material AD crosslinks a plurality of the fibers to bond the fibers to each other, thereby forming the fibers into a sheet shape. The additive material AD includes a resin that functions as a bonding material that binds the fibers together and specifically includes a thermoplastic resin and/or a thermosetting resin. A thermoplastic core-sheath resin may be included. Also, the additive material AD may include a coloring agent, an aggregation inhibitor, a flame retardant, and the like in addition to the aforementioned resins.

As the thermoplastic resin, a resin with a melting temperature of equal to or greater than 60° C. and equal to or less than 200° C. and with a deformation temperature of equal to or greater than 50° C. and equal to or less than 180° C., for example, can be used. Here, the deformation temperature can also be referred to as a glass transition temperature. As the thermoplastic resin, a petroleum-derived resin, biomass plastic, biodegradable plastic, or natural resin can be used. Here, examples of the petroleum-derived resin include a polyolefin-based resin, a polyester-based resin, a polyamide-based resin, polyacetal, polycarbonate, modified polyphenylene ether, cyclic polyolefin, an ABS resin, polystyrene, polyvinyl chloride, polyvinyl acetate, polyurethane, a Teflon resin, an acrylic resin, polyphenylene sulfide, polytetrafluoroethylene, polysulfone, polyether sulfones, amorphous polyarylate, a liquid crystal polymer, polyether ether ketone, thermoplastic polyimide, and polyamideimide. Examples of biomass plastic and biodegradable plastic include a polylactic acid, polycaprolactone, modified starch, polyhydroxybutyrate, polybutylene succinate, polybutylene succinate, and polybutylene succinate adipate. Examples of the natural resin include rosin. Teflon is a registered trademark. Examples of thermosetting resin include a phenolic resin, an epoxy resin, a vinyl ester resin, unsaturated polyester, and the like and a natural thermosetting resin such as shellac. The additive material AD contains one or more of the aforementioned resins. For example, a plurality of resins with different glass transition temperatures Tg and melting points may be contained.

The resin contained in the additive material AD is preferably in the form of particles or fiber. When a particulate resin is used, particles with a weight average particle diameter of equal to or greater than 0.1 μm and equal to or less than 120 μm are more preferably used, and particles with a weight average particle diameter of equal to or greater than 1 μm and equal to or less than 50 μm or are further preferably used.

The additive material AD may contain a resin material or a polymer material that forms a porous structure through heating, in addition to the aforementioned resins. These materials are, for example, thermally expandable materials that expand through heating. So-called foaming materials can be used as the thermally expandable materials. The thermally expandable materials are preferably in the form of particles, and the thermally expandable materials molded in the form of particles can be referred to as foaming particles. The particle diameter of the foaming particles contained in the additive material AD is preferably equal to or greater than 0.5 μm and equal to or less than 1000 μm and is more preferably equal to or greater than 1 μm and equal to or less than 300 μm in terms of a weight average particle diameter before foaming. The weight average particle diameter after foaming is further preferably equal to or greater than 5 μm and equal to or less than 1000 μm and is most preferably equal to or greater than 5 μm and equal to or less than 800 μm.

As the foaming particles, a capsule-shaped thermally expandable capsule that expands due to heat or a foaming material mixed particles into which a thermally expandable material is mixed can be used. Examples of thermally expandable capsules include Advancell manufactured by Sekisui Chemical Co., Ltd., Kureha microsphere manufactured by Kureha Co., Ltd., Expancel manufactured by Akzo Nobel Co., Ltd., and Matsumoto Microsphere manufactured by Matsumoto Yushi-Seiyaku Co., Ltd. Advancell, Kureha microsphere, Expancel, and Matsumoto Microsphere are registered trademarks. The foaming material mixed particles are a particulate preparation manufactured by mixing a thermally expandable material with the aforementioned thermoplastic resin. Here, as the foaming material, azodicarbonamide, N, N′-dinitrosopentamethylenetetramine, 4,4′-oxybis (benzenesulfonylhydrazide, N, N′-dinitrosopentamethylenetetramine, azodicarbonamide, or sodium hydrogen carbonate, for example, can be used.

When the surfaces of the foaming particles are covered with the resin, the coverage of the foaming particles with the resin is preferably equal to or greater than 10% and equal to or less than 100%.

The additive material AD may contain an inorganic filler, rigid fiber, or thixotropic fiber, in addition to the aforementioned resin, as a reinforcing material that makes the crosslinked structure in which the fiber is bound together more rigid. As the inorganic filler, calcium carbonate or mica, for example, can be used. As the rigid fiber, carbon fiber, glass fiber, or metal fiber, for example, can be used. Also, high-rigidity fiber such as Kevlar or other aramid fiber can be used. Kevlar is a registered trademark. Examples of thixotropic fiber include cellulose nanofiber.

Also, the additive material AD may be formed as a composite resin material powder by kneading and pulverizing the aforementioned constituents such as the resin, the foaming particles, and the reinforcing material.

1-2. Manufacturing Step of Fiber Structure

FIG. 2 is a flowchart illustrating a manufacturing step of the fiber structure to which the present disclosure is applied. The manufacturing step illustrated in FIG. 2 includes a step of manufacturing the sheet S1 using the sheet manufacturing apparatus 100.

Step SA1 is a crushing step of crushing the raw material MA and corresponds to a process performed by the crushing portion 12 of the sheet manufacturing apparatus 100, for example. The crushing step is a step of cutting the raw material MA into a size that is equal to or less than a predetermined size. The predetermined size is, for example, 1 cm to 5 cm square. When the raw material MA is supplied in a cut state, Step SA1 can be omitted.

Step SA2 is a defibration process and corresponds to a process performed by the defibrating portion 20 of the sheet manufacturing apparatus 100, for example.

Step SA3 is a step of taking out the material composed mainly of fiber from the defibrated material MB and is referred to as a separation step. The separation step is a step of separating particles such as a resin and an additive from the defibrated material MB including fiber and resin particles and taking out a material containing fibers as a main constituent. The separation step corresponds to a process including the sorting portion 40 and the rotating body 49 of the sheet manufacturing apparatus 100, for example.

When the raw material MA supplied in step SA1 does not contain particles or the like that affect the manufacturing of the sheet S1, or when it is not necessary to remove the particles or the like from the constituents contained in the raw material MA, the separation step in Step SA3 can be omitted. In this case, the defibrated material MB is used as it is as the fiber material MC.

Step SA4 is an addition step and is a step of adding the additive material AD to the fiber material MC separated in Step SA3. The addition step corresponds to, for example, the process performed by the additive supply portion 52 of the sheet manufacturing apparatus 100.

Step SA5 is a mixing step and is a step of manufacturing the mixture MX by mixing the fiber material MC with the additive material AD. The mixing step corresponds to, for example, a process performed by the mixing portion 50 of the sheet manufacturing apparatus 100.

Step SA6 is a sieving step and is a step of sieving the mixture MX to disperse it in the atmosphere and lowering it. The sieving step corresponds to, for example, the process performed by the dispersing portion 60 of the sheet manufacturing apparatus 100.

Step SA7 is an accumulation step and is a step of accumulating the mixture MX lowered in the sieving step in Step SA6 to form a web. The accumulation step corresponds to, for example, a process of forming the second web W2 by the second web forming portion 70 of the sheet manufacturing apparatus 100.

Step SA8 is a pressurizing and heating step, in which the web is pressurized and heated. The heating and pressurizing step corresponds to, for example, a process of heating and pressurizing the second web W2 by the processing portion 80 of the sheet manufacturing apparatus 100 and forming the sheet S1 through the pressurized sheet SS1 and the heated sheet SS2. Although the order of pressurization and heating in the pressurizing and heating step is not limited, the pressurization is preferably performed first.

Step SA9 is a molding step of molding the fiber structure using the sheet S1. In the molding step, a box-shaped fiber structure is produced by processes such as coupling, joining, and adhering performed on the sheets S1. In the molding step, a plurality of sheets S1 are joined, and it is thus possible to use construction methods such as adhesion with an adhesive material, thermal fusion using melting of a thermoplastic resin, skewering with a core material, and binding with a fastening component, and simple joining using roughness of the fiber surface of the sheet S1 may be employed.

The manufacturing step illustrated in FIG. 2 is not limited to the case where the sheet manufacturing apparatus 100 is used, and it is a matter of course that the sheet S1 manufactured by another apparatus can be used. The manufacturing step in FIG. 2 illustrated as a method of manufacturing the sheet S1 is an example, and the sheet S1 manufactured by another method may be used to mold the fiber structure to which the present disclosure is applied.

1-3. Fiber Orientation Direction in Sheet

FIG. 3 is an explanatory diagram of the fiber orientation direction in the sheet S1.

As indicated by the reference sign A in FIG. 3, the sheet S1 is a sheet with a thin planar shape or flexibility. The sheet S1 is obtained by sieving and accumulating a mixture of fiber contained in a defibrated material obtained by defibrating the raw material MA and a particulate and/or fibrous resin. Therefore, on the assumption of an X-Y-Z orthogonal coordinate system with the plane of the sheet S1 included as an X-Y plane, fiber F contained in the sheet S1 is directed in random directions in the X-Y plane while being directed in the direction along the plane of the sheet S1 in the Z direction. The pieces of fiber F contained in the sheet S1 are laminated and overlaps each other, or alternatively, the fiber F comes into point contact with other fiber F to have a structure with a certain orientation.

Therefore, since the fiber F is in the plane of the X-Y plane of the sheet S1, it is possible to state that the X-Y plane is the orientation direction of the fibers F in the sheet S1.

Further, directions of the fiber F may be unevenly distributed in the X-Y plane of the sheet S1. When the sheet S1 is manufactured by the sheet manufacturing apparatus 100, the step of accumulating the mixture MX on the mesh belt 72 with rotation of the cylindrical drum portion 61 is performed. In this accumulation step (Step SA7), the fiber contained in the mixture MX is likely to be oriented in the direction along the rotation direction of the drum portion 61. Therefore, the second web W2 tends to contain a lot of fiber F with an orientation along the rotation direction of the drum portion 61. Therefore, the sheet S1 also contains a lot of fiber F oriented in the rotation direction of the drum portion 61.

Here, the direction of the fiber F is indicated by the reference sign B in FIG. 3. The fiber F typically has a thin and long shape. The size of the fiber F in the longitudinal direction can be referred to as a fiber length L1, and the size of the fiber F in the shorter side direction can be referred to as a width L2. The width L2 corresponds to a fiber diameter. In this embodiment, the direction of the length L1 of the fiber F is referred to as the orientation direction DF. The orientation direction DF indicates the direction of one piece of fiber F.

The fiber orientation direction DS in the sheet S1 can be obtained by integrating the orientation directions DF of the plurality of the fibers F contained in the sheet S1. For example, a predetermined number of fibers F are extracted from the fiber F forming the sheet S1, an average orientation of the orientation directions DF of the plurality of extracted fibers F is obtained, and the obtained orientation can be regarded as the fiber orientation direction DS in the sheet S1.

As a method for obtaining the fiber orientation direction DS, the inventors used a digital microscope (VHX5000 manufactured by Keyence Corporation) to observe the surface of the sheet S1 or the fiber structure or the fiber structure block, which will be described later, under conditions of equal to or greater than 200-fold magnification and equal to or less than 500-fold magnification. The inventors randomly selected 50 fibers F from the fiber F observed with the digital microscope, measured the orientation directions DF with respect to the observed surfaces, calculated an average value, and regarded the average value as the fiber orientation direction DS.

More specifically, it is possible to obtain a proportion of the number of fibers in a predetermined direction by setting the number of fibers F with orientation directions DF being the predetermined direction to T1, setting the number of fibers F with orientation directions DF being different from the predetermined direction to T2, and obtaining T1/T2. Then, the predetermined direction in which the proportion of the number of fibers is the largest can be regarded as the fiber orientation direction DS in the sheet S1.

An example of the fiber orientation direction DS in the sheet S1 is indicated by the reference sign C in FIG. 3. The sheet S1 has a smaller size in the Z direction indicating the thickness than the size in the X-Y plane. Therefore, the fiber orientation direction DS in the sheet S1 is the direction within the X-Y plane as illustrated in FIG. 3 in most cases. The fiber orientation direction DS can be a fiber orientation directions DS3 and DS4 that are inclined with respect to the X axis and the Y axis or other directions in addition to a fiber orientation direction DS1 that is parallel to the Y axis and a fiber orientation direction DS2 that is parallel to the X axis.

Further, a method of matching the orientation directions DF of a lot of fiber F with the fiber orientation direction DS in the sheet can be exemplified. FIG. 4 is an explanatory diagram of a fiber orientation direction DS in a sheet S2. The sheet S2 is a member cut out from a laminated body 201 in which a plurality of sheets S are laminated along a cutting plane CU so as to have a sheet shape.

The laminated body 201 is formed by laminating the plurality of sheets S or folding the sheet S so that a plurality of layers are in an overlapping state and subjecting the sheets S or sheet S to a joining process. The bonding process is a press process, a pressurizing process and a heating process, a heating process in an oven or a furnace, an adhesive process with an adhesive, or the like.

In the sheet S2, fiber F extending in the X direction is cut into a short length due to the laminated body 201 being cut in the Y-Z plane. Also, the laminated body 201 does not contain long fiber F extending in the Z direction. Therefore, the fiber orientation direction DS in the sheet S2 is parallel to the Y direction in the drawing, and most of the fiber F that does not follow the fiber orientation direction DS is short fibers.

In the sheet S2, the orientation directions DF of a lot of fiber F is parallel to the fiber orientation direction DS, and the orientation directions DF are in a well-ordered state.

1-4. Buffering Function of Fiber Structure

Here, a buffering function and the fiber orientation direction DS of the fiber structure will be described.

FIG. 5 is a diagram illustrating a configuration of a test piece used for a buffering function test. Here, the buffering function means an action of absorbing or mitigating impact so that the impact is not transmitted from the fiber structure to other objects when the impact is applied to the fiber structure molded using the sheet S.

The present inventors produced a test piece 210 and a test piece 220 using the sheet S1 or the sheet S2 and measured stress and compressibility when an external force was applied to the test piece 210, 220. As a comparison target, a test piece 230 made of styrofoam was produced, and measurement similar to that for the test pieces 210 and 220 was conducted. FIG. 5 illustrates the test pieces 210, 220, and 230, and the direction in which an external force is applied in the test is indicated by the reference sign PW.

The test piece 210 has a substantially rectangular parallelepiped shape and has a surface 211 to which the external force PW is applied in the test. The fiber orientation direction DS in the test piece 210 intersects the direction of the external force PW at an angle of greater than 45 degrees and is typically perpendicular thereto. In other words, the fiber orientation direction DS perpendicularly intersects the normal line of the surface 211. The density of the test piece 210 was 0.15, and the content of the resin of the additive material AD contained in the test piece 210 was 30% by weight.

The test piece 220 has a substantially rectangular parallelepiped shape and has a surface 221 to which an external force PW is applied in the test. The fiber orientation direction DS in the test piece 220 forms an angle within 45 degrees with respect to the direction of the external force PW and is typically parallel thereto. In other words, the fiber orientation direction DS is parallel to the normal line of the surface 211. The density of the test piece 220 was 0.15, and the content of the resin of the additive material AD contained in the test piece 220 was 30% by weight.

The test piece 210 and the test piece 220 can be manufactured by laminating and joining the sheet S1 or the sheet S2.

The test piece 230 is an object with a substantially rectangular parallelepiped shape made of styrofoam and has a surface 231 to which the external force PW is applied in the test.

FIG. 6 is a chart illustrating test results of the buffering function. The horizontal axis in FIG. 5 represents the compressibility while the vertical axis represents the stress. The compressibility indicates the amount of compression of the test pieces 210, 220, and 230 in the external force PW direction due to the application of the external force PW as proportions to the sizes of the test pieces 210, 220, and 230. The stress is a stress of the test pieces 210, 220, and 230 against the external force PW.

A curve 251 in FIG. 6 is a compressibility-stress curve of the test piece 210, and a curve 252 is a compressibility-stress curve of the test piece 220. A curve 253 is a compressibility-stress curve of the test piece 230.

Also, FIG. 6 illustrates a curve 254 which is a compressibility-stress curve of a test piece as a control example. The curve 254 is an example using a test piece in which the orientation direction DF of the fiber F is disordered, that is, the orientation direction DF is not biased in a specific direction or has a small bias. This test piece is configured of the sheet S1 manufactured at a low density by the sheet manufacturing apparatus 100 so that the orientation direction DF is dispersed, has a density of 0.09, and contains 33% by weight of the resin of the additive material AD.

The curves 251 and 254 indicate increases in stress with increases in compressibility. In other words, since the stress against the external force PW increases as the surface 211 is depressed due to the external force PW, the surface 211 is compressed by the external force PW and has a higher density.

On the other hand, the curve 253 indicates a small increase in stress with an increase in compressibility. In other words, the test piece 230 made of styrofoam has a trend that the stress does not increase even if the surface 231 is deformed and depressed due to the external force PW. The curve 252 indicates a trend similar to the curve 253 as a whole and indicates a trend that an increase in stress with respect to an increase in compressibility is small.

Based on the results of the curves 252 and 253, the test piece 220 and the test piece 230 are deformed when a pressing force or an impact is applied thereto from the outside, but have a trend that the stress does not increase or is unlikely to increase during the deformation process. Therefore, it is possible to state that even if a packaging material or a storage container is deformed or destroyed when an external force or an impact is applied in a state in which an accommodated article is accommodated in the packaging material or the storage container using materials similar to those of the test piece 220 and the test piece 230, the force is unlikely to applied to the accommodated article. A storage container made of styrofoam is evaluated to have an excellent buffering function, and the test piece 220 is similarly suitable for manufacturing a packaging material or a storage container having an excellent buffering function. On the other hand, it is possible to state based on the result of the curve 251 that when an external force or an impact is applied to a packaging material or a storage container configured of a material similar to that of the test piece 210 in a state in which an accommodated article is accommodated therein, the force or the impact is likely to be applied to the accommodated article as well.

FIG. 7 is a schematic diagram illustrating expression states of the buffering functions of the test pieces 210, 220, and 230.

As illustrated in FIG. 7, it is considered that the test piece 210 was compressed by the external force PW in a state in which the fiber F overlapped each other, the hardness and the rigidity thus increased as the compressibility increased, and the stress was expressed. On the other hand, it is considered that the fiber F in the test piece 220 that received the external force PW moved in the DV direction so as to avoid the external force PW, and the entire test piece 220 was thus largely deformed and yielded to the external force PW. In this case, since an impact energy of the external force PW is consumed to disaggregate the fiber contained in the test piece 220 from a state in which the fibers are bonded with the bonding material with the deformation of the test piece 220, the external force PW is mitigated or absorbed. Also, since the test piece 220 is deformed in a direction different from the external force PW, the density of the test piece 220 is unlikely to increase even if the external force PW is applied thereto. Therefore, an increase in stress with the deformation is unlikely to occur. Also, it is considered that since the individual particles of the styrol resin in the test piece 230 made of styrofoam collapse due to the external force PW, rigidity of the entire test piece 230 does not change, and the stress is unlikely to increase.

As described above, the fiber structure using the sheet S1 and the sheet S2 can realize excellent buffering functions as a container made of styrofoam in a case in which the fiber orientation direction DS is parallel or nearly parallel to the direction in which the external force PW or the impact is applied.

According to the knowledge of the inventors, a high buffering function can be obtained in a case in which the fiber orientation direction DS forms an angle of equal to or greater than −45 degrees and equal to or less than +45 degrees with respect to the direction in which the external force PW or the impact acts.

In the following description, the sheet S1 and the sheet S2 will be referred to as a sheet S when they are not distinguished from each other. In other words, various structures configured using the sheet S in the following description may be produced using the sheet S1 as a material or the sheet S2 as a material.

1-5. Configuration Example of Fiber Structure

Here, a configuration example of a fiber structure using the sheet S will be described.

FIG. 8 is a perspective view of a fiber structure 300 as a configuration example using the sheet S. The fiber structure 300 is a substantially rectangular parallelepiped box having a bottom surface 301, side surfaces 302, 303, 304, and 305, and a top surface 306.

At least one or all of more than one of the side surfaces 302, 303, 304, and 305 are configured using the sheet S. Two or more of the side surfaces 302, 303, 304, and 305 are more preferably configured of the sheet S, and all the four side surfaces are further preferably configured of the sheet S. Note that in a case in which a plurality of surfaces of the fiber structure 300 is configured of the sheet S, the sheet S1 and the sheet S2 may be used together.

On the other hand, the bottom surface 301 and the top surface 306 may be configured of the sheet S. Also, a material other than the sheet S may be used as long as the material is a plate material with rigidity, and for example, the material may be a sheet or a plate made of a synthetic resin, a paper, a wooden material, or a metal plate.

In FIG. 8, the fiber orientation directions DS in the bottom surface 301, the side surfaces 302, 303, 304, and 305, and the top surface 306 are illustrated by arrows.

The inside of the fiber structure 300 is an accommodation space for accommodating an accommodated article. The fiber structure 300 can exhibit a buffering effect on the external force PW applied from the outside of the fiber structure 300, attenuate the external force PW, and protect the accommodated article. Here, the external force PW is an impact force or a pressing force and may include both.

FIG. 8 illustrates, as an example, a case in which the external force PW is applied from the outside toward the bottom surface 301. In this example, the bottom surface 301 corresponds to the outer surface to which the external force PW is applied. The external force PW is applied to the side surfaces 302, 303, 304, and 305 via the bottom surface 301. Also, it is possible to state that the external force PW is applied directly to the side surfaces 302, 303, 304, and 305 when the external force PW is applied to a peripheral edge of the bottom surface 301.

Here, the fiber orientation direction DS of each of the side surfaces 302, 303, 304, and 305 forms an angle of about 0 degree with the external force PW. Therefore, the side surfaces 302, 303, 304, and 305 can exhibit the buffering effect against the external force PW and attenuate the external force PW as described above in regard to the test piece 220.

The direction of the external force PW when the buffering effect is exhibited is not limited to the example illustrated in FIG. 8. In other words, when the external force PW is applied at an angle within 45 degrees with respect to the normal line of the bottom surface 301, the side surfaces 302, 303, 304, and 305 exhibit the buffering action against the external force PW.

FIG. 8 illustrates an example in which the bottom surface 301 and/or the top surface 306 is made of the sheet S. In this example, the fiber orientation direction DS in the bottom surface 301 and the fiber orientation direction DS in the top surface 306 are oriented in the same direction. Thus, when the external force PW is applied from a direction within 45 degrees with respect to the normal line of the side surface 303 or the side surface 305, the bottom surface 301 and/or the top surface 306 exhibits the buffering effect.

FIG. 9 is a perspective view illustrating a fiber structure 310 as another configuration example of the fiber structure using the sheet S. FIG. 10 is a sectional view taken along the line X-X in FIG. 9 and illustrates a section of the fiber structure 310.

The fiber structure 310 is a substantially rectangular parallelepiped box having a bottom surface 311, side surfaces 312, 313, 314, and 315, and a top surface 316. Inside the fiber structure 310, an internal structure 320 is disposed. The internal structure 320 is a substantially rectangular parallelepiped box having a bottom surface 321, side surfaces 322, 323, 324, and 325, and a top surface 326. The internal structure 320 is supported on the bottom of the fiber structure 310 via slope members 331, 332, 333, and 334. The bottom surface 321 of the internal structure 320 is located away from the bottom surface 311.

A material other than the sheet S may be used for the bottom surface 311, the side surfaces 302, 303, 304, and 305, and the top surface 306 of the fiber structure 310 as long as the material is a plate material with rigidity, and for example, the material may be a sheet or a plate made of a synthetic resin, a paper, a wooden material, or a metal plate. These surfaces may be made of the sheet S.

At least one of the slope members 331, 332, 333, and 334 is configured using the sheet S. Two or more surfaces are more preferably made of the sheet S, and all the four surfaces are further preferably made of the sheet S. Note that when a plurality of surfaces of the slope members 331, 332, 333, and 334 are made of the sheet S, the sheet S1 and the sheet S2 may be used together.

In the embodiment, an example in which all the slope members 331, 332, 333, and 334 are made of the sheet S is illustrated, and the fiber orientation direction DS in each of the slope members 331, 332, 333, and 334 is indicated by an arrow in the drawing.

The internal structure 320 forms an accommodation space for accommodating an accommodated article. The accommodated article accommodated in the internal structure 320 is supported by the slope members 331, 332, 333, and 334 via the bottom surface 321.

The fiber structure 310 has an effect of exhibiting a buffering effect against the external force PW applied from the outside of the fiber structure 310 toward the bottom surface 311, attenuating the external force PW, and protecting the accommodated article accommodated in the internal structure 320.

In this example, the bottom surface 311 corresponds to the outer surface to which the external force PW is applied. The slope members 331, 332, 333, and 334 indirectly receive the external force PW via the bottom surface 311 and exhibit a buffering action against the external force PW.

In the sectional view in FIG. 10, a case in which the external force PW is applied in the normal line direction of the bottom surface 311 is assumed. When the size of an angle θ1 in the direction of the external force PW with respect to the fiber orientation direction DS in the slope member 331 is within 45 degrees, the slope member 331 exhibits a buffering action as described above for the test piece 220 as an example and attenuates the external force PW. Even if the angle θ1 is larger than 45 degrees, the buffering effect of the slope member 331 is exhibited. However, when |θ1|≤45°, the buffering effect is satisfactorily exhibited, and the accommodated article inside the internal structure 320 can be protected.

Similarly, the slope member 333 exhibits an excellent buffering effect and attenuates the external force PW when the size of an angle θ2 in the direction of the external force PW with respect to the fiber orientation direction DS in the slope member 333 is within 45 degrees or when |θ2|≤45°.

The fiber structure 300 has a configuration using the sheet S for the outer surface to which the external force PW is applied directly or indirectly. On the other hand, the fiber structure 310 has a configuration using the sheet S for the internal structure to which the external force PW is applied indirectly. In both the cases, the sheet S exhibits the buffering effect, and the accommodated article can be protected. When the fiber orientation direction DS in the sheet S is within 45 degrees with respect to the direction of the external force PW, in particular, a satisfactory buffering effect is exhibited.

FIG. 11 is a perspective view illustrating a fiber structure 350 as yet another configuration example of the fiber structure using the sheet S. Specifically, a tubular body 401 as a processed example of the sheet S and the fiber structure 350 produced using the tubular body 401 are illustrated.

The tubular body 401 is a structure obtained by rolling the sheet S into a tubular shape. The tubular body 401 may be a tube with a circular section, an oval section, or a polygonal section. There may be a portion in which a plurality of sheets S overlap each other in the tubular body 401. The fiber orientation direction DS in the tubular body 401 is, for example, a direction along the axial direction of the tubular body 401 as illustrated in FIG. 11.

The tubular body 401 is disposed inside the fiber structure 350. The fiber structure 350 is a substantially rectangular parallelepiped box having a bottom surface 351, side surfaces 352, 353, 354, and 355, and a top surface 356. The tubular body 401 is secured to at least one of the bottom surface 351 and the top surface 356 and is preferably secured to both the bottom surface 351 and the top surface 356.

FIG. 11 illustrates, as an example, a case in which the external force PW is applied from the outside toward the bottom surface 351. In this example, the bottom surface 351 corresponds to the outer surface to which the external force PW is applied. The external force PW is applied indirectly to the tubular body 401 via the bottom surface 351. Since the fiber orientation direction DS of the tubular body 401 forms an angle within 45 degrees from the direction of the external force PW, the tubular body 401 exhibits a buffering effect against the external force PW while being deformed. Therefore, when the accommodated article is accommodated in the internal space of the tubular body 401, it is possible to attenuate the external force PW delivered to the accommodated article and to protect the accommodated article.

Also, when the side surfaces 352, 353, 354, and 355 of the fiber structure 350 are made of the sheet S, each of the side surfaces 352, 353, 354, and 355 exhibits a buffering effect along with the tubular body 401. Therefore, it is possible to more reliably protect the accommodated article from the external force PW.

1-6. Examples of Constituents Configuring Sheet

Examples of the material forming the sheet S include a combination of a cellulose fiber contained in the raw material MA and one or a plurality of types of additive materials AD.

With this configuration, a crosslinked structure between the cellulose fibers is formed through heating in the process for manufacturing the sheet S, air gaps between fiber structures are retained in the sheet S, and rigidity can be provided to the fiber structures. Further, the resin constituents of the additive materials AD that do not contribute to the crosslinked structure have an effect of enhancing rigidity of the fiber by coating the surface of the fiber therewith.

Further, the crosslinked structure of the fiber serves as a minute deformation region in a case in which the external force PW is applied thereto, absorbs an impact or an energy of the applied external force PW, discharge the impact or the energy as a thermal energy, and mitigates the impact or the energy. This leads to an effect of exhibiting functions such as an impact absorption function and absorption of noise as an internal loss. As described above, when the stress against the energy of the external force PW is exhibited with the configuration in which the fiber orientation direction DS is located within the range of equal to or greater than −45 degrees and equal to or less than +45 degrees with respect to the direction of the external force PW, energy mitigation of the crosslinked structure in the fiber is more effectively caused.

As examples of the composition forming the sheet S, a first composition example, a second composition example, a third composition example, a fourth composition example, and a fifth composition example will be exemplified.

The first composition example includes a cellulose fiber derived from the raw material MA, a first particulate resin, and a second particulate resin.

In the first composition example, the first particulate resin and the second particulate resin causes the manufactured sheet S to maintain a heat melting property. Therefore, there is an advantage that a plurality of sheets S can easily be joined through heating when the sheets S are joined as will be described later.

The second composition example includes a cellulose fiber derived from the raw material MA, a first particulate resin, and a second fibrous resin. In the second composition example, an effect that the second fibrous resin fixedly joins the cellulose fibers can be expected. Further, since the first particulate resin is contained, the manufactured sheet S maintains thermal superiority. Therefore, there is an advantage that a plurality of sheets S can easily be joined through heating when the sheets S are joined as will be described later.

The first resin and the second resin are selected from the aforementioned thermoplastic resin and thermosetting resin, and at least one of the first resin and the second resin preferably contains the thermoplastic resin.

Either the first resin or the second resin can be a biodegradable resin. In this case, it is possible to provide the sheet S and the fiber structure with less environmental burden. When one of the first resin and the second resin is a resin with high water resistance, the other can be a water-soluble resin. In other words, the sheet S with water resistance can be realized using the water-soluble resin.

The third composition example includes cellulose fiber derived from the raw material MA, a first particulate resin, and a third fibrous resin. The third resin is selected from the aforementioned resin materials or polymer materials that form a porous structure through heating. With this configuration, the third resin can secure large gaps in the cellulose fibers crosslinked with the first resin. Therefore, it is possible to expect that the ability to absorb the impact energy is further enhanced.

The fourth composition example includes a cellulose fiber derived from the raw material MA, a first resin and/or a second resin, and inorganic particles. The inorganic particles are selected from the aforementioned inorganic fillers such as calcium carbonate and mica, for example.

The fifth composition example includes a cellulose fiber derived from the raw material MA, a first resin and/or a second resin, and inorganic fiber or high-rigidity fiber. The inorganic fiber or high-rigidity fiber is selected from the aforementioned rigid fiber and thixotropic fiber.

The inorganic particles in the fourth composition example and the inorganic fiber or high-rigidity fiber in the fifth composition example have the effect of enhancing the stress of the sheet S against the energy of the external force PW. Therefore, the sheet S and the fiber structure with higher buffering performance can be realized.

Further, a material other than the additive materials AD may be dispersed in the accumulation step for forming the second web W2 in the step for manufacturing the sheet S made of the first to fifth composition examples. In this case, a specific material can be unevenly distributed on the surface of the sheet S. An effect of enhancing a joining property when the plurality of sheets S are joined can be expected by dispersing a thermoplastic resin that functions as a bonding material, for example. Also, there is an advantage that the sheet S can be effectively colored by dispersing a resin or inorganic particles containing a coloring constituent, for example.

1-7. Configuration of Composite Sheet

The aforementioned sheets S1 and S2 may be used as they are for the fiber structures 300, 310, and 350, or may be used as a composite sheet in which a plurality of sheets S1 and S2 are joined.

FIG. 12 illustrates composite sheets 411, 412, 413, 414, 415, and 416 as examples using rectangular sheets S11, S12, S13, and S14 obtained by molding the sheet S1 or the sheet S2 into rectangular shapes. FIG. 13 illustrates composite sheets 421, 422, 423, 424, 425, and 426 as examples using rectangular sheets S14 and S15 obtained by molding the sheet S1 or the sheet S2 into rectangular shapes.

Since the sheets S1 and S2 can be easily cut, rectangular sheets S11 to S15 with different lengths and widths can be obtained. The composite sheet 411 can be obtained by laminating and joining two of the rectangular sheets. Also, the composite sheets 412, 413, 414, 415, and 416 can be obtained by laminating and joining three or four of the rectangular sheets S11, S12, S13, and S14. Moreover, the composite sheets 421, 422, 423, 424, 425, and 426 can be obtained using longer rectangular sheet S15.

Pressurization, a combination of pressurization and heating, and the like can be exemplified as methods for joining the rectangular sheets S11 to S15, as described above, and heating using an oven, water vapor heating, microwave heating, and the like can be exemplified as heating methods.

The composite sheets 411 to 416 and 421 to 426 illustrated in FIGS. 12 and 13 have different fiber orientation directions DS. Therefore, it is possible to exhibit a buffering effect against the external force PW applied from various directions. In other words, these composites 411 to 416 and 421 to 426 have a plurality of fiber orientation directions DS that form an angle of 90 degrees with each other. Therefore, the external force PW forms an angle within 45 degrees with respect to any of the fiber orientation directions DS regardless of directions from which the external force PW is applied. Therefore, exhibition a high buffering effect against the external force PW applied from various directions can be expected.

The rectangular sheets S16 and S17 illustrated in FIGS. 14 and 15 have a fiber orientation direction DS that is an oblique direction with respect to the sides of the outer shapes of the rectangular sheets S16 and S17. In an example, the rectangular sheets S16 and S17 have a fiber orientation direction DS that forms an angle of 45 degrees with the sides of the outer shapes.

The composite sheets 431, 432, 435, 436, and 437 formed using these rectangular sheets have a plurality of fiber orientation directions DS different from each other by 45 degrees or 90 degrees. Therefore, a buffering effect is exhibited against the external force PW from a wide range of angles.

In this manner, when the fiber structures 300, 310, and 350 are formed using the composite sheets obtained by combining a plurality of sheets S1 and/or sheets S2, it is possible to realize the fiber structures that have a buffering effect against the external force PW from a wide range. The fiber structures formed using these composite sheets will particularly be referred to as fiber structure blocks.

As described above, the fiber structure 300 to which the present disclosure is applied includes the sheet S including the cellulose fiber disposed such that the main fiber orientation direction DS is the first direction and the crosslinking material for binding a plurality of the cellulose fibers to each other. The first direction forms an angle of equal to or less than 45 degrees with respect to the direction of the external force PW applied from the outside to the outer surface of the fiber structure 300.

With this configuration, since the fiber orientation direction DS in the sheet S forms an angle of equal to or less than 45 degrees with respect to the external force PW, the sheet S exhibits the buffering effect due to the effect of the fiber contained in the sheet S being disassembled. Therefore, when a container for accommodating an accommodated article is formed of the fiber structure to which the present disclosure is applied, for example, it is possible to protect the accommodated article from impact.

The fiber structure 300 includes the cellulose fiber disposed such that the main fiber orientation direction DS is the first direction, the crosslinking material for binding a plurality of the cellulose fibers to each other, and the fiber structure 300 has an accommodation space that accommodates an accommodated article therein, and the first direction forms an angle of equal to or less than 45 degrees with respect to the direction of the external force PW applied from the outside of the fiber structure 300 toward the accommodation space.

With this configuration, since the fiber orientation direction DS in the sheet S forms an angle of equal to or less than 45 degrees with respect to the external force PW, the sheet S exhibits the buffering effect due to the effect of the fiber contained in the sheet S being disassembled. Therefore, it is possible to protect the accommodated article in the accommodation space from an impact.

The first direction of the fiber orientation direction DS is a direction that forms an angle of equal to or less than 45 degrees with respect to the direction of the external force PW applied directly to the outer surface of the fiber structure 300 or applied to the outer surface of the fiber structure 300 via an external member. With this configuration, since the fiber structure is deformed due to the external force PW and exhibits a strong buffering effect, it is possible to mitigate an impact of the external force PW.

Also, since the fiber structure 300 has a plurality of outer surfaces and the first direction forms an angle of equal to or less than 45 degrees with respect to a normal line of any one of the outer surfaces, it is possible to exhibit a high buffering effect against the external force PW applied from the outside of the fiber structure 300.

Since the first direction in the fiber structure 300 forms an angle of equal to or less than 45 degrees with respect to the normal line of the bottom surface 301, which is the largest outer surface among the plurality of outer surfaces, it is possible to exhibit a high buffering effect against the external force PW applied from the normal line direction of the bottom surface 301.

The crosslinking material contained in the sheet S includes a first resin and a second resin made of a material different from the first resin. In this case, it is possible to firmly join the fiber contained in the sheet S due to characteristics of the plurality of resins and thereby to provide functions such as water resistance and reduction of an environmental burden.

The sheet S may include a material different from the cellulose fiber and the crosslinking material. In this case, it is possible to provide, to the sheet S, functions such as improvement in joining property and improvement in impact resistance as well as coloring and the like of the sheet S.

A configuration using a composite sheet as a flat plate structure with laminated cellulose fibers for the fiber structure 300 may be employed, and in this configuration, the first direction may be a direction included in the plane of the flat plate structure. In this case, it is possible to realize the fiber structure 300 having a plurality of fiber orientation directions DS including the first direction. Therefore, it is possible to exhibit a high buffering effect against the external force PW applied from various directions.

2. Second Embodiment

As a second embodiment to which the present disclosure is applied, an example in which a fiber structure is formed through molding the sheet S using a mold will be described.

FIG. 16 is a schematic diagram illustrating a process performed by the molding portion 120. The molding portion 120 has an upper mold 121 and a lower mold 122 and forms a fiber structure 500 by sandwiching and pressurizing the sheet S1 or the sheet S2 between the upper mold 121 and the lower mold 122. The molding portion 120 may be formed as a part of the sheet manufacturing apparatus 100, or may be a device separate from the sheet manufacturing apparatus 100.

The molding portion 120 may be able to sandwich a plurality of sheets S in an overlapping manner between the upper mold 121 and the lower mold 122. The upper mold 121 and the lower mold 122 may be a male mold and a female mold that fit to each other, or may be a mold in which a gap is formed between the upper mold 121 and the lower mold 122.

Also, the molding portion 120 may be configured to perform heating during or after pressurization on the sheet S with the upper mold 121 and the lower mold 122. In this case, a method of raising a temperature of an entire chamber including the molding portion 120 using a heater or a method of incorporating a heater in the upper mold 121 and/or the lower mold 122 can be employed as a heating method. Also, a method of heating the pressurized fiber structure 500 with a heater or through microwave heating may be used.

FIG. 17 is a perspective view illustrating a fiber structure 510 as a specific example of the fiber structure 500.

The fiber structure 510 has a conical projecting portion 511 and a flat surface portion 512 around the projecting portion 511. When the fiber structure 510 is used as a packaging material or a storage container that accommodates an accommodated article, the distal end of the projecting portion 511 abuts on the accommodated article. The fiber structure 510 exhibits a buffering effect against the external force PW applied from the normal line direction of the flat surface portion 512.

FIG. 18 is a sectional view taken along the line XVIII-XVIII of FIG. 17 and illustrates a cut surface passing through the apex of the projecting portion 511.

As illustrated in FIG. 18, at least one direction of the slope of the projecting portion 511 overlaps the fiber orientation direction DS. In this case, the slope of the projecting portion 511 preferably forms an angle θ3 within 45 degrees with respect to the external force PW applied from the normal line direction of the flat surface portion 512. In other words, |θ3|≤45°. In this case, when the external force PW is applied to the fiber structure 510, the external force PW acts on the projecting portion 511 at an angle within 45 degrees. Therefore, there is an effect that the projecting portion 511 attenuates the external force PW.

The fiber structure 510 may be obtained by laminating a plurality of sheets S and processing the laminated sheets S using the molding portion 120. Also, a configuration in which the inside of the projecting portion 511 is dense may be used.

FIG. 19 is a perspective view illustrating a fiber structure 550 as another example of the fiber structure 500 according to the second embodiment.

The fiber structure 550 has a truncated cone-shaped base portion 551 and a flat surface portion 552 around the base portion 551. The apex portion 553 of the base portion 551 is a flat surface. When the fiber structure 550 is used as a packaging material or a storage container that accommodates an accommodated article, the accommodated article is placed on the apex portion 553.

The fiber structure 550 exhibits a buffering effect against the external force PW applied from the normal line direction of the flat surface portion 552. Therefore, the fiber orientation direction DS preferably follows the slope forming the base portion 551, and the slope of the base portion 551 is preferably within 45 degrees with respect to the normal line direction of the flat surface portion 552.

The base portion 551 exhibits a buffering effect against the external force PW and also has an effect of stabilizing the accommodated article in the accommodated state due to the apex portion 553 being a flat surface.

Furthermore, a configuration in which a plurality of base portions 551 are disposed in an aligned manner can also be employed.

FIG. 20 is a perspective view illustrating a fiber structure 560 as yet another specific example of the fiber structure 500. The fiber structure 560 includes a plurality of base portions 551 and a flat surface portion 562 around the base portions 551. The base portions 551 are configured similarly to that in the fiber structure 550.

The fiber structure 560 can support an accommodated article with the plurality of base portions 551 and is thus suitable for a packaging material or a storage container that accommodates a heavy article.

The aforementioned fiber structures 510, 550, and 560 have effects similar to those described in the first embodiment as the fiber structure and the fiber structure block according to the present disclosure.

3. Other Embodiments

Each of the aforementioned embodiments is just a specific aspect for carrying out the present disclosure described in the aspects, is not intended to limit the present disclosure, and can be carried out in various aspects as described below, for example, without departing from the gist thereof.

For example, the sheet S illustrated in each of the aforementioned embodiments is not limited to a sheet with a smooth surface and may have a rough surface obtained through embossing or shaving. The fiber structure and the fiber structure block made using the sheet S are not limited to the fiber structures 300, 310, and 350. In other words, the shape having the outer surfaces is not limited to the rectangular parallelepiped shape and may be a spherical shape or a polyhedron. Further, the fiber structures 510, 550, and 560 may be formed into box shapes, may be molted inside rectangular parallelepiped structures such as the fiber structure 300, or may be molded into spherical shapes, and the shapes are not limited to a specific shape.

It is a matter of course that other detailed configurations can be changed in any manner. 

What is claimed is:
 1. A fiber structure comprising: a cellulose fiber disposed such that a main fiber orientation direction is a first direction; and a crosslinking material that binds a plurality of cellulose fibers to each other, each of which is the cellulose fiber disposed such that the main fiber orientation direction is the first direction, wherein the first direction forms an angle of equal to or less than 45 degrees with respect to a direction of an external force applied from an outside to an outer surface of the fiber structure.
 2. A fiber structure comprising: a cellulose fiber disposed such that a main fiber orientation direction is a first direction; and a crosslinking material that binds a plurality of cellulose fibers to each other, each of which is the cellulose fiber disposed such that the main fiber orientation direction is the first direction, wherein the fiber structure has an accommodation space that accommodates an accommodated article therein, and the first direction forms an angle of equal to or less than 45 degrees with respect to a direction of an external force applied from an outside of the fiber structure toward the accommodation space.
 3. The fiber structure according to claim 1, wherein the first direction is a direction that forms an angle of equal to or less than 45 degrees with respect to a direction of an external force applied directly to the outer surface of the fiber structure or applied to the outer surface of the fiber structure via an external member.
 4. The fiber structure according to claim 1, wherein the fiber structure has a plurality of outer surfaces, each of which is the outer surface to which the external force is applied from the outside, and the first direction forms an angle of equal to or less than 45 degrees with respect to a normal line of any one of the outer surfaces.
 5. The fiber structure according to claim 4, wherein the first direction forms an angle of equal to or less than 45 degrees with respect to a normal line of a largest outer surface of the plurality of outer surfaces.
 6. The fiber structure according to claim 1, wherein the crosslinking material contains a first resin and a second resin made of a material that is different from the first resin.
 7. The fiber structure according to claim 1, wherein the fiber structure includes a material that is different from the cellulose fiber and the crosslinking material.
 8. The fiber structure according to claim 1, wherein the fiber structure is configured of a flat plate structure in which the cellulose fibers are laminated, and the first direction is a direction included in a plane of the flat plate structure.
 9. A fiber structure block comprising: a plurality of combinations of fiber structures each including a cellulose fiber disposed such that a main fiber orientation direction is a first direction and a crosslinking material that binds a plurality of cellulose fibers to each other, each of which is the cellulose fiber disposed such that the main fiber orientation direction is the first direction, wherein the fiber structure block has an accommodation space that accommodates an accommodated article therein, and the fiber structures are disposed such that the first direction forms an angle of equal to or less than 45 degrees with respect to a direction of an external force applied from an outside toward the accommodation space. 